Various miniature fiber optic grating encoders that use fiber optic receiver channels are known, including those disclosed in U.S. Pat. Nos. 6,906,315; 7,053,362; and 7,126,696, (hereinafter “the '315, '362, and '696 patents”) each of which is hereby incorporated herein by reference in its entirety. Such miniature encoders offer a desirable combination of features, which may include extremely small size, very high accuracy, electrical noise immunity, and very high speed operation.
Many motion control and/or position measurement systems, or the like, include provisions for inputting a reference signal that is usable to identify a particular period within a grating scale. The reference signal, generally corresponding to a feature that is fixed relative to the grating scale, provides a reference point that eliminates the position ambiguities that may otherwise arise in incremental type displacement measuring systems, which count signal periods as a basis for long range measurements.
However, a reference signal generating configuration that is easily and economically combinable with miniature fiber optic grating encoders such as those included in the above references, and that provides similar desirable features, is not known. Such a reference signal generating configuration would be desirable.